This serves as a continuation of my previous article Fasting: The Miracle Cure. The article was published about a month ago and since then I have been asked many questions about the benefits of intermittent fasting (IF) and the role of IF in weight loss and health. I have decided to write this article to address the most frequently asked questions.

Fasting can be beneficial to our health and well-being. It’s been used for thousands of years as a way to increase a person’s awareness of food and to improve concentration and mental sharpness. Now, it’s coming back into the popular consciousness, as people are starting to realize what a powerful tool it is for weight loss and better health.

There are countless benefits of fasting that can be used to help aid in weight loss, healthy cholesterol levels, and even immune system health. A period of fasting will significantly reduce your caloric intake and help to reset your metabolism, which can help you shed some weight naturally.. Read more about fasting and hormone imbalance and let us know what you think.


It’s important to look at the physiology of what occurs in our bodies when we don’t eat in order to properly comprehend fasting and its advantages. Here’s a quick primer.


The body’s primary energy sources are glucose and fat. Glucose is the body’s most easily accessible fuel source. If glucose isn’t available, the body may adjust by switching to fat metabolism, which has no detrimental health implications.

It’s an unavoidable aspect of life. Low-food-availability periods have always existed throughout human history, and methods have developed to cope with this aspect of Paleolithic existence. There are many phases in the shift from fullness to hunger.

  1. Insulin levels increase during meals due to diet. This enables glucose to be taken in and utilized directly for energy generation by tissues such as muscles and the brain. Excess glucose is stored as glycogen in the liver.
  2. The post-absorption phase occurs 6 to 24 hours after the fast has begun. Insulin levels start to fall. Glucose is released for energy when glycogen is broken down. Glycogen reserves are only good for approximately 24 hours.
  3. Gluconeogenesis takes anywhere from 24 hours to 2 days. Gluconeogenesis is the process by which the liver generates new glucose from amino acids. It literally translates to “creating new glucose.” Blood sugar levels fall in individuals who do not have diabetes, but they stay within the usual range.
  4. Ketosis occurs 2 to 3 days after you begin fasting. Lipolysis, or the breakdown of fat to generate energy, is stimulated by the low insulin levels obtained during fasting. Triglycerides, a kind of fat that is stored, are broken down into a glycerol base and three fatty acid chains. For gluconeogenesis, glycerol is utilized. Many tissues in the body can utilize fatty acids as an energy source directly, but the brain cannot. Ketones are fatty acids that may pass the blood-brain barrier and are used by the brain. Ketone bodies provide approximately 75% of the energy needed by the brain after four days of fasting. Beta-hydroxybutyrate and acetoacetate are the two major kinds of ketone bodies generated, with beta-hydroxybutyrate increasing by more than 70-fold while fasting.
  5. Protein Preservation Phase – >5 days – High levels of growth hormone ensure preservation of muscle mass and lean tissue. The energy required to maintain basic metabolism is provided almost exclusively by free fatty acids and ketones. High levels of noradrenaline (adrenaline) prevent a decrease in metabolic rate.

During gluconeogenesis (step 3), you’ll see that the protein is utilized to produce glucose for a while. Many people take this to imply that the body uses muscle as a source of glucose. The truth is very different. Excess protein is broken down to generate glucose during this period. It isn’t always muscular, however. Connective tissues, skin, aged cells, and other undesirable cell components may all be eliminated. This is an autophagy process whose significance is just now being realized.

The body subsequently restores the essential proteins that were eaten during this breakdown period. The cell renewal cycle is now complete. It’s similar to a kitchen remodel. It’s not possible to simply replace the existing cabinets with new ones. You must first remove the old, ineffective one. As a result, cell regeneration necessitates the breakdown of old proteins. You’ll miss the whole helpful update cycle if you just concentrate on failures.

When there is a lack of food, the human body has well-developed systems to cope. Essentially, we’re discussing the shift from glucose (short-term) to fat (long-term) burning (long term). The body stores energy in the form of fat. When there is a shortage of food, stored food is released to fill the gap. So, until fat stores are exhausted, the body does not burn muscle for fuel.


If this is true, we must think that the human body is so badly constructed that we store dietary energy as glucose and fat yet utilize protein as soon as the food supply runs out. Is it a? It’s the same of stockpiling firewood for the winter and then cutting the bank and burning it as soon as the temperature drops, leaving all of the wood intact. Consider all the indigenous, Inuit, and tribal peoples who have been afflicted by famine and hunger on many occasions. Wouldn’t they be fat globules at 100% if they burnt all the muscle? It’s amusing because it never happened.

Hormonal balancing


Fasting is the most reliable and effective way to decrease insulin levels. This remark was made many decades ago and is generally believed to be correct. It’s straightforward and straightforward. Insulin levels are raised by all diets. Avoiding all meals is the most efficient approach to decrease this level. As the body starts to burn fat for energy, blood sugar levels stay normal. During a fasting period of 24 to 36 hours, this impact is seen. Fasting for a long time decreases insulin levels even further. Alternate daily fasting has recently been investigated as a viable way of lowering insulin levels.

Fasting on a regular basis has been proven to increase insulin sensitivity as well as decrease insulin levels. This is the piece of the weight-loss jigsaw that has been lacking. Most diets decrease the quantity of high-insulin foods consumed, but they do not address the issue of insulin resistance. Insulin resistance causes weight loss at first, but insulin levels and body weight remain high. Fasting is a powerful tool for lowering insulin resistance.

Insulin reduction helps the body rid itself of extra salt and water. In the kidneys, insulin promotes salt and water retention. Diuresis, or the loss of excess water, is common with Atkins diets, implying that the first weight loss is mostly water. While it is true that diuresis aids in the reduction of stomach bloating and dizziness. A small decrease in blood pressure is also seen by some individuals. Weight loss is also found to be rapid during the onset of fasting. Weight loss averaged 0.9 kg per day over the first five days, significantly surpassing calorie restriction and most likely owing to salt and water diarrhea.

Hormone of growth

Growth hormone has been shown to enhance the availability and utilization of fat as a source of energy. It also aids in the preservation of muscle mass and bone density. Growth hormone secretion diminishes as people become older. Starvation is one of the most potent triggers for the production of growth hormone. Growth hormone production more than doubled during the five-day fast. During the fasting phase, the net physiological impact is the preservation of muscle and bone mass.


The cell renewal cycle is completed by this growth hormone wave. Long-term research on intermittent fasting indicate that it is more than four times better than calorie restriction for preserving lean body mass %.


During Lent, it is improper to be concerned about malnutrition. Because fat stores are very substantial, a shortage of calories is not a major reason for worry. The development of micronutrient deficiencies is the primary issue. Long-term hunger experiments, on the other hand, have shown no indications of malnutrition.

Potassium levels may decrease somewhat, but even two months of fasting without supplements does not reduce them to less than 3.0 mEq/L. This is a considerably longer Lenten period than is usually advised. During fasting, magnesium, calcium, and phosphorus levels remain constant. This is most likely owing to the bones’ high stores of these minerals. The bones store 99 percent of the calcium and phosphorus in the body.

A daily dosage of micronutrients is provided by taking a multivitamin. The multivitamin alone sustained the 382-day therapeutic fast, with no negative health consequences. In fact, the guy said that he felt fantastic throughout the procedure. The modest rise in uric acid reported while fasting may be the sole reason for worry.


Noradrenaline levels increase, providing us with the energy to consume more calories. Fasting for 48 hours, for example, results in a 3.6 percent boost in metabolism rather than the feared metabolic halt. Resting energy expenditure rose by 14% in response to a 4-day fast. Your body speeds up your metabolism instead of slowing it down. This is most likely to ensure that we have enough energy to locate food.

It’s a fascinating topic. Fasting, but not a low-calorie diet, causes a slew of hormonal shifts that are advantageous on many levels. Starvation causes the body to switch from burning sugar to burning fat. At rest, the metabolic rate does not decrease; rather, it increases. Essentially, we eat our own fat to fuel our bodies. We consume our own fat. It’s very logical. Fats are basically food that has been preserved. Studies have even shown that epinephrine (adrenaline) burns fat without decreasing blood sugar.

Remember how we spoke about how insulin works before? Sugar and fat are the two energy storage mechanisms in diet. In the liver, sugar is made up of glucose and glucose chains (glycogen). It’s similar to your refrigerator. Food may be easily brought in and out, but storage space is restricted. The body utilizes glucose first because it is much simpler to use.

Fat is a kind of food that can be kept for a long time, such as. In a freezer, for example. Food is more difficult to get into and out of the freezer, but storage is limitless. The issue with our weight reduction is that we can’t seem to get the freezer to empty. Our bodies will be unable to access fat stores if they are still accustomed to burning sugar. Then you feel hungry and want to stock the fridge with food. Even if there is plenty of food stored as fat in the freezer, we are hungry.

Fasting while emptying the refrigerator is one option. As a result, it’s simple to go into the freezer and burn fat. Fasting is a convenient method to lose weight.

Jason Fung, Ph.D.

The benefits of intermittent fasting are no secret, but it’s not just about weight loss and deeper sleep. In fact, fasting affects almost every aspect of your physiology, from energy, fatigue and immunity to hormones, insulin sensitivity, and even cognition.. Read more about fasting physiology pdf and let us know what you think.

Frequently Asked Questions

What are the physiological effects of fasting?

The physiological effects of fasting are the result of a lack of food. Fasting can have many different effects on the body, but usually it is associated with weight loss and other health benefits.

Does fasting increase hormones?

Yes, fasting can increase the levels of hormones in your body.

Can fasting help with hormone imbalance?

There is no scientific evidence that fasting can help with hormone imbalance.

This article broadly covered the following related topics:

  • intermittent fasting and hormones
  • fasting and estrogen dominance
  • physiological effects of fasting
  • physiology of fasting
  • fasting and hormones
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